My prior applications for U.S. Letter Pat. Ser. No. 608,576, filed Aug. 28, 1975, now U.S. Pat. No. 3,949,745 allowed Apr. 13, 1976, and Ser. No. 642365, filed Dec. 19, 1975, disclose and claim, among other features, parenteral fluid administration sets utilizing a floating siphon whose longer siphon leg operates within an upright open-ended rigid overflow tube and has length such that in certain positions of floating siphon travel, depending upon the level of the parenteral fluid in a container (which may be a flow regulator chamber connected to and receiving the parenteral fluid to be administered intravenously from an inverted bottle or similar type rigid container or a disposable plastic bag), its outlet end projects through and outwardly from the lower open end of said rigid overflow tube, said projecting end being provided with means for priming the siphon and/or for altering the calibre of the siphon.
While my aforesaid disclosed parenteral fluid administration sets are fully operative and effectively serve the purpose for which they were intended, recent experiments with variant devices have given indication that floating-siphon type administration sets employing a siphon U-tube whose longer leg is relatively short to the degree that its outlet end terminates a substantial distance above the bottom of said container and which further makes unnecessary the rigid overflow tube aforesaid, may constitute a practical and effective alternate construction, provided that in place of the rigid overflow tube, a fluid-flow tube fashioned of a material which renders the tube non-rigid axially and also radially collapsible under the pressure of the fluid content of the container in which said tube is immersed, with means for maintaining a flow path through said tube as the fluid level recedes, be utilized in place thereof.